Duct Pressure Testing Overview For Builders [Video]

Date Published: April 6, 2020


Is A Duct Pressure Test Required On Your Next Project?

Energy codes may have changed in your area, and the city and county you are building in may now require a duct pressure test on your HVAC system.

Although this test has been utilized for a while, many areas of Colorado are adopting newer codes that have more stringent duct leakage requirements.

If the process is new to you, then we made this overview video for you. It provides a brief overview of a duct pressure test, suggests some best practices, and reviews the equipment and process.

The Duct Leakage Test.

A duct leakage test is similar to a blower door test. A blower door test uses a large fan placed within a door frame to de-pressurize a home and measure the total air leakage.

A duct pressure test does the same thing but within the home’s duct system. The supplies and returns are sealed with tape, and the system is pressurized or depressurized to determine the total duct leakage of the duct system.

This is done by connecting a fan assembly to the air handler or a large return and then measuring the pressure difference between the interior and exterior of the duct system.

On average the test takes approximately 2 hours, and it is typically done right before drywall is hung. This way you have full access to the duct system if issues are found.

Seal Everything!

The fan and meter we use are extremely sensitive. The amount of pressure used throughout the system is not very high, but the manometer is very sensitive. Because of this, even marginal duct sealing will likely fail the system.

We recommend going above and beyond on your sealing efforts. This includes all seams, connections, lateral joints on trunks, 45 and 90 degree angles, and around every boot. See more examples in the video above.

Duct Pressure Testing: Poorly sealed seams

The boot seems to be one of the most commonly missed areas. The testing requirements state that the boot is part of the sealed system, so we can only tape the top. So if the home has 20+ unsealed boots, that can be a significant source of air leakage.

Duct Pressure Testing: Boot sealing needed

Finally, although you could test the system before the furnace/air handler is installed, you would need to test the supply and return side separately, which could lead to inaccurate results. We always recommend that testing be performed after the furnace is installed.

When Is A Duct Leakage Test Required?

We have a whole blog dedicated to this topic here. However, if it is required in your jurisdiction, it is typically only required when the ducts are located outside the heated envelope of the home.

This means if you have duct running through an attic, unconditioned crawlspace, or a garage, you will likely be required to perform this test.

These rules may be changing as Denver County is considering requiring a pressure test regardless of where the ducts are run. Subscribe to our newsletter to stay updated on code changes!

Duct Testing After Drywall

Although you should avoid it, the test can be performed after drywall is hung. The same process takes place, but repairs are much harder to address.

However, there is a product called Aero-Seal that can be sprayed into the duct system to seal all the gaps. The manufacturer guarantees the dust system will pass inspection after the product is applied.

We hope that this article gives you a brief overview of duct leakage testing. To learn more about our duct leakage testing services in Colorado, visit our service page here.

If you have further questions, our energy services team will be happy to answer them. Give us a call or leave a comment below!

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About the Author: Chris Scott

Chris Scott is an ASHI certified home inspector with multiple years of experience in home inspections, blower door testing, duct leakage testing, and Boulder Rental License Inspections. Chris is also the Website Coordinator for Scott Home Inspection.

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